Optical waveguides are used to propagate light from one point to another and are of increasing interest for use in optical communications systems. The light is propagated along a material that has a higher refractive index than surrounding material. Because of its high refractive index and excellent electro-optic properties, lithium niobate has been of interest in making thin film waveguides. Heretofore lithium niobate has been deposited on suitable substrates, such as lithium tantalate, by several methods; by sputtering, by chemical vapor deposition; and by epitaxial growth by melting technique. These methods attempt to form a layer or film of single crystal lithium niobate in the substrate. These methods are tedious and lack reliability, and the resultant waveguides have relatively high losses in the optical transmission of light.